Tap changer with a polarity switch for a variable transformer

Abstract

The invention relates to a step switch provided with a preselector and a polarity circuit, a separate polarization resistance being respectively provided at the beginning and the end of the stepped winding. Optionally, the two polarization resistances can be connected continuously or via separate polarity switches.

The invention claimed is: 
     
       1. In combination:
 a regulating transformer having a main winding having an end and a tap winding having a start, an end, and a plurality of taps; 
 a tap changer connected to a load shunt and selectably connectable to the taps; 
 a preselector connected to the start and end of the tap winding and to the end of the main winding; 
 a first polarity resistor connected between the start of the tap winding and the load shunt; and 
 a second polarity resistor connected between the end of the tap winding and the load shunt. 
 
     
     
       2. The combination defined in  claim 1 , further comprising:
 a changeover switch connected between the load shunt and the tap changer. 
 
     
     
       3. The combination defined in  claim 1 , further comprising:
 respective first and second openable switches connected in series with the first and second resistors between the start and end of the tap winding and the load shunt. 
 
     
     
       4. The combination defined in  claim 1 , wherein the first and second polarity resistors have different electrical values.